A PC-BSD® installation assumes that you have an existing primary partition to install into. If your computer has only one disk and PC-BSD® will be the only operating system, it is fine to accept the default partitioning scheme. However, if you will be sharing PC-BSD® with other operating systems, care has to be taken that PC-BSD® is installed into the correct partition; otherwise, you may inadvertently overwrite an existing operating system.

If you wish to install multiple operating systems on your computer, you will need the following:

a partition for each operating system. Many operating systems, including PC-BSD®, can only be installed into a primary partition. This means that you will need to use partitioning software as described in Partitioning the Hard Drive/9.2.

a boot loader that allows you to select which operating system you wish to boot into. Depending upon the choice of boot loader and the operating systems that you install, you may or may not have to configure the boot loader to list all of the installed operating systems. Also, depending upon the order that you install the operating systems, the existing MBR data may be overwritten. This section will describe the configuration of several different boot loaders and how to restore an overwritten MBR.

a backup of any existing data. This backup should not be stored on your computer's hard drive but on another computer; on removable media, such as a USB drive; or burnt onto a DVD media. If you are careful in your installation, everything should go fine. However, you will be glad that you made a backup should something go wrong.

Choosing the Installation Partition

When installing PC-BSD® onto a computer that is to contain multiple operating systems, care must be taken to select the correct partition in the Disk Selection screen of the installation. On a system containing multiple partitions, each partition will be listed. Highlight the partition that you wish to install into and make sure that you do not select a partition that already contains an operating system or data that you wish to keep.

make sure that you click the "Customize" button while in the "Disk Selection" screen. If you just click Next without customizing the disk layout, the installer will overwrite the contents of the primary disk.

GRUB Boot Loader

If you install PC-BSD® on a computer that already contains an operating system, an entry for PC-BSD® will automatically be added to the PC-BSD® boot menu. Depending upon which other operating systems are installed, the installer may or may not automatically detect and add entries for the other operating systems.

If your other operating system is not found, use the PC-BSD® Bug Reporting tool to create a bug report. Include the version of the missing operating system and on which disk and partition that operating system is installed. If you are already familiar with how to create GRUB entries and are successful in manually adding an entry, include that entry in your bug report. This way, other PC-BSD® users with similar layouts can benefit when the required GRUB entry is added to the installer's logic.